While the PCB is heated, part of the free volume of water can be dissipated through the microporous PCB substrate, thereby reducing the molar volume fraction of water that may accumulate at the voids or microcracks, which is beneficial to the explosion of the PCB. improve. However, if the surface of the PCB has a large area of copper foil pattern coverage, when the PCB is heated, the large copper foil surface above the buried hole blocks the water vapor that escapes outward after being heated, so that the pressure of water vapor in the microcrack increases, resulting in occurrence of The chance of a burst is greatly increased.

Obviously, the sufficient and necessary conditions for the latent burst must be induced by the temperature factor. Optimizing the reflow soldering temperature profile based on a comprehensive analysis of specific product characteristics is effective in suppressing the occurrence of cracking

Analysis of CPU assembly defects